1. Field of the Invention
Two previously known active agents are covalently linked into a particularly constructed hybrid ligand for preventing or treating cancer in animals or humans, particularly breast cancer in mammals.
2. Description of Related Art
Both tamoxifen and melatonin are known active agents; both are also known for certain anti-cancer effects. Tamoxifen is already known in the prior art to treat: a) women diagnosed with hormone-receptor-positive, early-stage breast cancer post procedure, to reduce recurrence; and b) women and men diagnosed with metastatic hormone-receptor-positive disease to produce regression and remission. Indeed, at this writing Tamoxifen is the world's largest selling drug for the treatment of breast cancer. Tamoxifen is also given at this writing to women who have not been diagnosed with breast cancer but whom are at higher-than-average risk for disease. It is generally accepted at this writing that Tamoxifen is not useful in treating hormone-receptor-negative breast cancer.
Melatonin has increasingly been understood as relevant to breast cancer in various ways. Certain studies show that as melatonin levels reduce after about age 40, risk for breast cancer also increases. Moreover, patient assays and laboratory experiments indicate both that lower levels of melatonin stimulate growth of breast cancer cells and that adding melatonin to these cells inhibits their growth. Daily melatonin administration has been shown in some studies to increase survival time of laboratory animals having untreated mammary tumors. Animals with mammary tumors also exhibited increased levels of prolactin and catecholamine concentrations compared to the healthy animals, and the administration of melatonin stabilized the hormone levels—returning the levels to those of healthy animals and suggesting that melatonin administration is therapeutic to hormone-receptor-positive cancer.
At this writing, however, experts in oncology generally agree that despite their significant benefits, neither tamoxifen nor melatonin presents an adequate active agent for preventing or treating hormone-receptor-related cancer taken alone. Breast cancer is currently the second leading cause of cancer deaths in women today. Excluding nonmelanoma skin cancers, breast cancer remains the most common cancer among women. According to the American Cancer Society, about 1.3 million women worldwide will be diagnosed annually with breast cancer and 465,000 will die of the disease. Accordingly, a need remains for a prevention and treatment approach that improves on available products and therapies.